1. Field of the Invention
The invention concerns a battery (cell, battery, etc) including an electrode assembly comprising at least two electrodes of opposite polarity and at least one separator.
2. Description of the Prior Art
In cylindrical batteries the spiral electrode assembly is obtained by winding the positive electrode and the negative electrode alternating with first and second separator layers. The separator insulates the positive electrode from the negative electrode and insulates the positive and negative exterior parts of the battery.
The electrode assembly is introduced into the cylindrical sealed metal casing. An electrolyte enabling ion exchange is introduced into the electrode assembly. A lid insulated from the casing is connected to the positive electrode, usually by welding, and forms the positive pole. An interior groove in the upper part of the casing locates the lid horizontally in the casing. The casing is crimped to the lid with a seal between them to seal the battery.
Short-circuiting of the cell by continuous or intermittent contact of the connection between the lid and the positive electrode with the top of the negative electrode must be avoided.
Such contact can occur during assembly of the cell, in which case it can be detected during in-production testing; however, it occurs mainly during normal charging and discharging of the cell due to thermal effects (expansion) and vibration. Short-circuits between the connection and the top of the electrode are associated with assembly problems such as:
the negative electrode shifting relative to the separator during winding, PA1 defective positioning of the lid during welding of the connection, and PA1 defective bending of the connection during closing of the lid.
Document JP-A-7 014 572 teaches the addition of an insulative washer above the electrode assembly to solve this problem. This solution has the drawback of requiring an additional manufacturing operation and of increasing the unit cost of the battery. Moreover, locating the washer correctly in the battery, whether manually or automatically, is not easy, given the presence of the connection, and defective location entails the risk of sealing problems or problems with locating the lid in the battery (tilting).
Document FR-2 094 491 describes a battery in which the conductive parts of the electrode project and are slit and bent perpendicularly to form a bearing surface resembling fish scales. The projecting ends of the separator are bent and engage to a greater or lesser degree between two consecutive scales, the effect of which is to enhance the elasticity of the bearing surface. This produces an overlap which makes it very difficult to impregnate the electrode assembly with the electrolyte and impedes the flow of gas during operation of the cell.
The aim of the invention is to propose a solution which avoids short-circuits but does not have the drawbacks mentioned above.